This invention relates in general to universal joints and in particular to an improved structure for a constant velocity type of universal joint.
A universal joint is a mechanical coupling device which provides a rotational driving connection between two rotatable shafts, while permitting such shafts to be oriented at an angle relative to one another. Universal joints are commonly used in the drive train systems of vehicles. For example, a universal joint is commonly used to provide a rotational driving connection between a drive shaft rotatably driven by a vehicle engine and an input shaft connected to the vehicle axle assembly. This is because the drive shaft and the axle assembly input shaft are rarely co-axially aligned. To accommodate this non-alignment, while still providing a rotational driving connection, a universal joint is provided therebetween.
Universal joints are commonly classified by their operating characteristics. One important operating characteristic relates to the relative angular velocities of the two shafts connected thereby. In a constant velocity type of universal joint, the instantaneous angular velocities of the two shafts are always equal, regardless of the angle of rotation. In a non-constant velocity type of universal joint, the instantaneous angular velocities of the two shafts vary with the angle of rotation (although the average angular velocities for a complete revolution are equal).
A typical structure for a constant velocity universal joint includes a cylindrical inner race connected to one of the shafts and a hollow cylindrical outer race connected to the other of the shafts. The outer surface of the inner race and the inner surface of the outer race have respective pluralities of grooves formed therein. The grooves extend linearly and have generally semi-circular cross sectional shapes. Each groove formed in the outer surface of the inner race is associated with a corresponding groove formed in the inner surface of the outer race. A ball is disposed in each of the associated pairs of grooves. The balls provide a driving connection between the inner and outer races. An annular cage is typically provided between the inner and outer races for retaining the balls in the grooves. The cage is provided with a plurality of circumferentially spaced openings for this purpose.
In one known variety of the ball and cage type of constant velocity joint, the grooves formed in the outer surface of the inner race are oriented so as to be alternately inclined relative to the rotational axis of the joint. Similarly, the grooves formed in the inner surface of the outer race are alternately inclined relative to the rotational axis of the joint. For each pair of associated inner and outer race grooves, the inner race groove is inclined in one direction relative to the rotational axis of the joint, while the outer race groove is inclined in the opposite direction. Thus, this variety of joint is commonly referred to as a cross groove constant velocity joint.
Known cross groove joints permit relative axial movement between the inner race and the cage, as well as between the cage and the outer race. Thus, the center of the joint (which is defined by the point of intersection of the rotational axes of the two shafts connected thereto) can move axially during use. Because there is no physical engagement between the inner race and the cage or between the cage and the outer race, cross groove joints have been found to be well suited for high rotational speed applications.
However, some applications for universal joints require the use of a fixed center type of joint, i.e., a joint wherein the point of intersection of the rotational axes of the two shafts cannot move axially during use. Although non-cross groove varieties of constant velocity joints are known which have fixed centers, some of those structures have been found to be not well suited for high rotational speed applications. Of those non-cross groove varieties which are suited for high rotational speed applications, it has been found to be inconvenient and uneconomical to manufacture two different types of joint structures, namely, the cross groove variety (which permits axial movement of the joint center) and the non-cross groove variety (which prevents such axial movement). Accordingly, it would be desirable to provide a cross groove variety of constant velocity joint which can be manufactured so as to be easily adapted for use having either a fixed center or an axially movable center.